ACL2 Characters

ACL2 accepts 256 distinct characters, which are the characters
obtained by applying the function code-char to each
integer from 0 to 255. Among these, Common Lisp designates certain
ones as *standard-characters*, namely those of the form
(code-char n) where n is from 33 to 126, together with
#\Newline and #\Space. The actual standard characters may
be viewed by evaluating the constant expression
*standard-chars*.

The standard character constants are written by writing a hash mark
followed by a backslash (#\) followed by the character.